0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 2 3 4 5 6 7 8 9 10 Number of cars Price (thousands of dollars) A B C D T = A + B + C + D S market clears at 7 cars, $7,000 ↕ At $7,000: A wants 2, B wants 1, C wants 2, D wants 2 — market demand 7. The four demands sum sideways to 7, exactly the seven cars available: the market clears.

Drag the dashed price line up or down (or focus it and use the arrow keys). Watch the four buyers’ demands add sideways into the market demand, and compare it to the seven cars available.